Refers to physical depth (water, holes, etc.) or abstract depth (thought, feeling, knowledge).
この川の深さはどれくらいですか。
How deep is this river?
彼の知識の深さには驚かされる。
I am amazed by the depth of his knowledge.
I measured the depth of this river.
His words have real depth to them.
This pool has a depth of two meters.
The more we discussed it, the more the depth of the problem grew.